1. Field of the Invention
The present invention relates to a carbon nanotube emitter and its fabrication method, and a Field Emission Device (FED) using the carbon nanotube emitter and its fabrication method.
2. Description of the Related Art
Once unique structural and electrical properties of carbon nanotubes were known, research has been performed for applying the carbon nanotubes to devices, such as Field Emission Devices (FEDs), transistors, and secondary batteries. In particular, the carbon nanotube used as an emitter of an FED has many advantages including low driving voltage, high luminance, high cost efficiency, and the like. Examples of methods of fabricating carbon nanotube emitters include screen printing that uses a carbon nanotube powder, and a method that uses Chemical Vapor Deposition (CVD). The carbon nanotube growth method that uses CVD has advantages that it make it possible to fabricate a high-resolution display device and has a simple process because it directly grows carbon nanotubes on a substrate. Thus, research in carbon nanotube growth is actively progressing. Representative examples of Chemical Vapor Deposition include Plasma Enhanced Chemical Vapor Deposition (PECVD) and thermal Chemical Vapor Deposition (CVD).
To fabricate improved FEDs, the carbon nanotubes used as the emitter should have a lower driving voltage and higher electron emission current and exhibit a uniform electron emission property over a wide area. To have a lower driving voltage and higher electron emission current, the carbon nanotubes should have a thinner diameter and a proper density. Since the diameter of the carbon nanotubes is determined by a size of a catalyst metal on the tube, it is necessary to form and control catalyst particles having a smaller size in order to synthesize carbon nanotubes having the thin diameter. Furthermore, in order to adjust the density of the carbon nanotubes, it is necessary for the grown carbon nanotubes to be unidirectional. To obtain a uniform electron emission property over the wide area, it is necessary for a growth system to provide a uniform temperature distribution.